Detection of Seismic Structural Damage

Damage analysis models based on equivalent modal parameters are used to identify the serviceability limit state for structures subjected to earthquake loads. A model for the analysis of seismic structural damage consists of a number of numerical indicators (damage indices) and of a procedure for their computation. A structure exhibits a nonlinear behavior when it experiences an earthquake. Nonetheless a time variant equivalent linear structure can be defined. Damage indices can be defined from the vibrational parameters of the equivalent linear structure considered. It is shown that the problem of identification of the serviceability limit state is equivalent to the problem of detection of seismic structural damage. A limit state can be defined as a surface in the space of the damage indices relative to the model considered. Experiments on small-scale models are analyzed to obtain an analytical definition of the serviceability limit state. Additional aspects of the subject are discussed.